Photosensitive resin composition, color filter, and copolymer resin useful for them

ABSTRACT

A color filter including a transparent substrate, a colored layer on the substrate, and a protective layer on the colored layer. The protective layer is the product formed by exposing, developing, and heating a coating containing an epoxy-containing copolymer resin having 0 to 55% by mole of formula (1), 5 to 95% by mole of formula (2), and 5 to 95% by mole of formula (3), the formula (1) units having been partially reacted, through carboxyl groups, with a (meth)acryloylalkyl isocyanate compound, the formula (2) units having been partially reacted, through hydroxyl groups, with a (meth)acryloylalkyl isocyanate compound, the copolymer resin containing 5 to 95% by mole of (meth)acryloyl groups, an acid value of 0 to 400 mg KOH/g, and a weight average molecular weight of 5,000 to 1,000,000:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a photosensitive resincomposition and a color filter provided with a protective layer formedof the photosensitive resin composition, and more particularly to acolor filter which can realize color liquid-crystal displays havingexcellent display quality and high reliability. The present inventionalso relates to a novel epoxy-containing copolymer resin usable in thephotosensitive resin composition.

[0003] 2. Background Art

[0004] In recent years, color liquid-crystal displays have drawnattention as flat displays. They generally have a structure comprising:a color filter; a counter electrode substrate facing the color filter;and a liquid-crystal layer provided in a gap (1 to 10 μm) between thecolor filter and the counter electrode substrate. The structure of thecolor filter is such that a colored layer of a black matrix and aplurality of colors (generally three primary colors, red (R), green (G),and blue (B)) or, in recent years, a color hologram is provided on atransparent substrate and a protective layer and a transparent electrodeare stacked thereon in that order. These color liquid-crystal displaysare constructed so that a color image is obtained by controlling thelight transmission of the liquid-crystal layer in its portionscorresponding to pixels of respective colored layers R, G, and B or acolor hologram.

[0005] In the color filter, the protective layer, when the color filtercomprises the colored layer, functions to protect and flatten the colorfilter. In general, color liquid-crystal displays have a problem thatthe presence of uneven gap attributable to the waviness of the surfaceof the transparent substrate in the color filter, uneven gap among R, G,and B pixels, or uneven gap within pixels of R, G, and B lowers theflatness of the transparent electrode. This causes uneven colors anduneven contrast, leading to lowered image quality. In particular, incolor liquid crystal displays of STN (super-twisted nematic) system, theflatness greatly affects the image quality. This renders flattening bythe protective layer very important.

[0006] In use, the color filter is adhered to the counter electrode. Theassembly is then tested for display quality. In consideration ofreutilizability of the color filter when the assembly is judged to beunacceptable in the display quality test, the protective layer ispreferably provided only in specific regions so as to cover the coloredlayers on the transparent substrate. To this end, the protective layerhas been formed using a photocurable resin which permits portions to becured to be easily limited through a mask.

[0007] In the formation of the protective layer using the conventionalresin, an organic solvent is used in the development after exposure.This is troublesome in handleability and wastewater treatment andfurther lacks in profitability and stability. In order to solve thisproblem, a photocurable resin has been developed which, by virtue of theintroduction of an acidic group into the photocurable resin, permitsalkali development after the exposure.

[0008] In this type of photosensitive resin composition, afterpatterning by ultraviolet irradiation, development with an alkali iscarried out, followed by heat treatment to prepare a color filter. Inthe development with an alkali, patterning is carried out through theaction of carboxyl groups in the copolymer resin. After the development,water resistance and alkali resistance are required of the copolymerresin. Therefore, the carboxyl group remaining in the photocured patternshould be heat treated in the presence of an epoxy resin or the like toimpart water resistance and pattern strength.

[0009] For this reason, the present inventors have proposed, in JapanesePatent Application No. 99240/1998, a copolymer resin which, as analkali-developable photocurable copolymer resin, enables alkali-solublegroups, such as carboxylic acid groups, and radically polymerizablegroups specifying curability, such as acryloyl group, to be regulated bytaking into consideration curability, alkali solubility and the like.Further, in Japanese Patent Application No. 216868/1998, the presentinventors have proposed a photosensitive resin composition comprisingthis alkali-developable photocurable copolymer resin and an epoxy resin,such as a cresol novolak type epoxy resin, and a color filter. However,the provision of a photosensitive resin composition possessing excellentcurability, alkali resistance and other properties and a color filter,which can be produced by a simple process, has excellent flatness, andcan realize highly reliable color liquid-crystal displays havingexcellent display quality, have been desired in the art.

SUMMARY OF THE INVENTION

[0010] Accordingly, it is an object of the present invention to providea photosensitive resin composition possessing excellent hot pure waterresistance, solvent resistance, heat resistance, alkali resistance,sensitivity, and pencil hardness and to provide a color filter which canbe produced by a simple process, has excellent flatness, and exhibitsexcellent display quality and reliability.

[0011] It is another object of the present invention to provide a novelepoxy-containing copolymer resin usable in the photosensitive resincomposition.

[0012] In order to attain the above objects of the present invention,according to one aspect of the present invention, there is provided anepoxy-containing copolymer resin comprising 0 to 55% by mole ofconstituent units represented by formula (1), 5 to 95% by mole ofconstituent units represented by formula (2), and 5 to 95% by mole ofconstituent units represented by formula (3), the constituent unitsrepresented by formula (1) having been partially reacted, throughcarboxyl groups thereof, with a (meth)acryloylalkyl isocyanate compound,the constituent units represented by formula (2) having been partiallyreacted, through hydroxyl groups thereof, with a (meth)acryloylalkylisocyanate compound, said copolymer resin containing 5 to 95% by mole of(meth)acryloyl groups and having an acid value of 0 to 400 mg KOH/g anda weight average molecular weight of 5,000 to 1,000,000 as determinedusing polystyrene as a standard:

[0013] wherein R represents hydrogen or an alkyl group having 1 to 5carbon atoms; R₁ represents an alkylene group having 2 to 4 carbonatoms; R₂ represents an alkylene group having 1 to 4 carbon atoms; Zrepresents a 1,2-epoxy, 1,3-epoxy, or 1,4-epoxy group; and a, b, and care integers respectively corresponding to said molar percentages.

[0014] Preferably, the copolymer resin further comprises 0 to 75% bymole of constituent units represented by formula (4) and 0 to 75% bymole of constituent units represented by formula (5):

[0015] wherein R represents hydrogen or an alkyl group having 1 to 5carbon atoms, R₂ represents an aromatic carbon ring, R₃ represents analkyl or aralkyl group, and d and e are integers correspondingrespectively to contents in terms of % by mole of the constituent units.

[0016] According to another aspect of the present invention, there isprovided a photosensitive resin composition comprising: the aboveepoxy-containing copolymer resin; an alkali-developable photocurablecopolymer resin; a bifunctional or higher polyfunctionalphotopolymerizable acrylate monomer; and an initiator,

[0017] the alkali-developable photocurable copolymer resin comprising 5to 55% by mole of constituent units represented by formula (1) and 5 to95% by mole of constituent units represented by formula (2), theconstituent units represented by formula (1) having been partiallyreacted, through carboxyl groups thereof, with a (meth)acryloylalkylisocyanate compound, the constituent units represented by formula (2)having been partially reacted, through hydroxyl groups thereof, with a(meth) acryloylalkyl isocyanate compound, the copolymer resin containing5 to 95% by mole of (meth)acryloyl groups and having an acid value of 5to 400 mg KOH/g and a weight average molecular weight of 5,000 to1,000,000 as determined using polystyrene as a standard.

[0018] In the photosensitive resin composition, preferably, thealkali-developable photocurable copolymer resin and the epoxy-containingcopolymer resin each further comprise 0 to 75% by mole of constituentunits represented by formula (4) and 0 to 75% by mole of constituentunits represented by formula (5).

[0019] According to a further aspect of the present invention, there isprovided a color filter comprising: a transparent substrate; a coloredlayer provided on the transparent substrate; and a protective layerprovided so as to cover the colored layer, the protective layer havingbeen formed by coating the above photosensitive resin composition,exposing the coating, developing the exposed coating with an alkali, andheating the developed coating.

[0020] As compared with conventional phenol novolak type epoxy resinsand the like, the epoxy-containing copolymer resin according to thepresent invention has higher miscibility with an alkali-developablephotocurable copolymer resin by virtue of the similarity of thestructure, and, when used in a protective layer of a color filter, uponcrosslinking at the time of heat curing, can form a pattern possessingexcellent strength, alkali resistance, and water resistance.

[0021] The photosensitive resin composition of the present invention, byvirtue of the use of an alkali-developable photocurable copolymer resinhaving controlled alkali solubility and curability and anepoxy-containing copolymer resin possessing excellent miscibility withthe alkali-developable photocurable copolymer resin, possesses excellenthot pure water resistance, solvent resistance, heat resistance, alkaliresistance, sensitivity, and pencil hardness. The use of thisphotosensitive resin composition in the formation of a protective layercan realize a color filter which can be produced by a simple process,has excellent flatness, and exhibits excellent display quality andreliability.

BRIEF DESCRIPTION OF THE DRAWING

[0022]FIG. 1 is a schematic diagram showing the construction of oneembodiment of the color filter according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The photosensitive resin composition of the present inventioncomprises an alkali-developable photocurable copolymer resin, anepoxy-containing copolymer resin, a bifunctional or higherpolyfunctional photopolymerizable acrylate monomer, and an initiator. Asdescribed below, the alkali-developable photocurable copolymer resin andthe epoxy-containing copolymer resin each basically contain constituentunits comprising (meth)acryloyl groups introduced into constituent unitsrepresented by formula (1) and constituent units comprising(meth)acryloyl groups introduced into constituent units represented byformula (2). If necessary, these copolymer resins may further containconstituent units represented by formula (4) and constituent unitsrepresented by formula (5). As used herein, the term “(meth)acryloylgroup” refers to a methacryloyl group or an acryloyl group, and the term“(meth)acrylic acid” refers to methacrylic acid or acrylic acid.

[0024] The epoxy-containing copolymer resin according to the presentinvention will be first described.

[0025] In formulae (1) to (5), R represents hydrogen or an alkyl grouphaving 1 to 5 carbon atoms. Examples of alkyl groups usable hereininclude methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, and n-pentyl groups.

[0026] The constituent unit represented by formula (1) is an optionalcomponent in the epoxy-containing copolymer resin. The epoxy-containingcopolymer resin containing the constituent units represented by formula(1), however, will be described by way of example. Monomers usable forintroducing the constituent units represented by formula (1) include,for example, acrylic acid, methacrylic acid, 2-carboxy-1-butene,2-carboxy-1-pentene, 2-carboxy-1-hexene, and 2-carboxy-1-heptene.According to the photosensitive resin composition using theepoxy-containing copolymer resin according to the present invention, thephotocurability and the alkali solubility are imparted by thealkali-developable photocurable copolymer resin described below. Theepoxy-containing copolymer resin also can improve the alkali solubilityby adding the constituent units represented by formula (1) thereto. Thecontent of the constituent units represented by formula (1) ispreferably such that the stability of the epoxy-containing copolymerresin is not deteriorated, that is, 0 to 55% by mole, preferably 5 to30% by mole.

[0027] The constituent units represented by formula (2) are basicallythose in which (meth)acryloyl groups are introduced. Examples of R₁include ethylene, propylene, and butylene groups. Specific examples ofmonomers usable for introducing the constituent units represented byformula (2) include 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate,4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate. Theconstituent units represented by formula (2) have been partially reactedthrough hydroxyl groups thereof with the (meth)acryloylalkyl isocyanatecompound to introduce (meth)acryloyl groups therein. The content of theconstituent units represented by formula (2) is regulated according tothe level of photopolymerizability required of the copolymer resin andis 5 to 95% by mole, preferably 10 to 50% by mole.

[0028] The constituent units represented by formula (3) are those forintroducing epoxy groups into the copolymer resin. In formula (3), R₂may represent an alkylene group having 1 to 4 carbon atoms, such as amethylene, ethylene, propylene, or butylene group; and Z may represent a1,2-epoxy, 1,3-epoxy, or 1,4-epoxy group. The constituent unitsrepresented by formula (3) may have, as a substituent, a bulky ballastgroup, such as an aromatic ring, which can improve the mechanicalproperties of the coating. Monomers usable for the introduction of theepoxy group into the copolymer resin include: oxetane acrylates, such asglycidyl methacrylate, (3-methyl-3-oxetanyl)methyl acrylate, and(3-ethyl-3-oxetanyl)methyl acrylate; oxetane methacrylates, such as(3-methyl-3-oxetanyl)methyl methacrylate, and (3-ethyl-3-oxetanyl)methylmethacrylate; and 2-tetrahydropyranyl acrylate and 2-tetrahydropyranylmethacrylate. Since the constituent units represented by formula (3) donot react with the (meth)acryloylalkyl isocyanate compound used in theintroduction of the (meth)acryloyl group into the constituent unitsrepresented by formulae (1) and (2), the epoxy group is left.

[0029] In the photosensitive resin composition containing theepoxy-containing copolymer resin according to the present invention, thecontent of the constituent units represented by formula (3) is regulatedby the amount of the carboxyl group left in the pattern after thedevelopment with an alkali. The content is 5 to 95% by mole, preferably10 to 50% by mole.

[0030] The epoxy-containing copolymer resin according to the presentinvention comprises the constituent units represented by formulae (1),(2), and (3). Other constituent units, which may be contained in theepoxy-containing copolymer resin, include constituent units representedby formulae (4) and (5).

[0031] The constituent units represented by formula (4) function toimpart coatability to the copolymer resin. Examples of R₂ usable hereininclude aromatic rings, such as phenyl and naphthyl groups. Monomersusable for introducing the constituent units represented by formula (4)include, for example, styrene and α-methylstyrene. The aromatic ring maybe substituted by a halogen atom, such as chlorine or bromine, an alkylgroup, such as a methyl or ethyl group, an amino group, such as an aminoor dialkylamino group, a cyano group, a carboxyl group, a sulfonic acidgroup, phosphoric acid group or the like. The content of the constituentunits represented by formula (4) is 0 to 75% by mole, preferably 5 to50% by mole.

[0032] The constituent units represented by formula (5) inhibit alkalidevelopment. Examples of R₃ usable herein include alkyl groups having 1to 12 carbon atoms and aralkyl groups, such as benzyl and phenylethylgroups. Monomers usable for introducing the constituent unitsrepresented by formula (5) include, for example, (meth)acrylic esters,such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, phenyl (meth)acrylate,cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate,dicyclopentanyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, benzyl(meth)acrylate, and phenylethyl (meth)acrylate. The content of theconstituent units represented by formula (5) is 0 to 75% by mole,preferably 5 to 50% by mole.

[0033] For the introduction of the constituent units represented byformulae (1) to (5), the monomers exemplified above respectively forthese constituent units may be used alone or as a mixture of two ormore.

[0034] Preferred polymerization solvents usable for the production ofthe copolymer resin comprising constituent units represented by formulae(1) to (5) include solvents free from active hydrogen, such as hydroxyland amino groups. Examples thereof include: ethers, such astetrahydrofuran; glycol ethers, such as diethylene glycol dimethylether, diethylene glycol diethyl ether, diethylene glycol methyl ethylether; cellosolve esters, such as methyl cellosolve acetate; propyleneglycol monomethyl ether acetate; and 3-methoxybutyl acetate. Aromatichydrocarbons, ketones, esters and the like are also usable.

[0035] Polymerization initiators commonly known as radicalpolymerization initiators may be used. Specific examples thereofinclude: azo compounds, such as 2,2′-azobisisobutylonitrile,2,2′-azobis-(2,4-dimethylvaleronitrile),2,2′-azobis-(4-methoxy-2,4-dimethylvaleronitrile); organic peroxides,such as benzoyl peroxide, lauroyl peroxide, tert-butyl peroxypivalate,and 1,1′-bis-(tert-butylperoxy)cyclohexane; and hydrogen peroxide. Whena peroxide is used as the radical polymerization initiator, the peroxidemay be used in combination with a reducing agent for use as a redox typepolymerization initiator.

[0036] In the production of the copolymer resin comprising constituentunits represented by formulae (1) to (5), molecular weight modifiers maybe used to modify the weight average molecular weight. Examples ofmolecular weight modifiers usable herein include: halogenatedhydrocarbons, such as chloroform and carbon tetrabromide; marcaptans,such as n-hexylmercaptan, n-octylmercaptan, n-dodecylmercaptan,tert-dodecylmercaptan, and thioglycolic acid; xanthogens, such asdimethylxanthogen disulfide and diisopropylxanthogen disulfide;terpinolene; and α-methylstyrene dimer.

[0037] The copolymer resin comprising constituent units represented byformulae (1) to (5) may be a random or block copolymer of monomers forthe constituent units represented by formulae (1) to (5). The randomcopolymer may be produced by adding dropwise a composition comprisingmonomers and a catalyst to a polymerizer containing a solvent at atemperature of 80 to 110° C. over a period of 2 to 5 hr, followed byripening.

[0038] The copolymer resin comprising the constituent units representedby formulae (1) to (5) has a weight average molecular weight, asdetermined using polystyrene as the standard (hereinafter referred tosimply as “weight average molecular weight” or “Mw”), in the range of5,000 to 1,000,000, an acid value of 0 to 400 mg KOH/g, and a hydroxylvalue of 5 to 400 mg KOH/g.

[0039] The epoxy-containing copolymer resin according to the presentinvention is obtained by reacting the copolymer comprising constituentunits represented by formulae (1) to (5) with a(meth)acryloyl-containing isocyanate compound.

[0040] The (meth)acryloylalkyl isocyanate compounds usable herein is onewherein a (meth)acryloyl group is bonded to an isocyanate group (—NCO)through an alkylene group having 2 to 6 carbon atoms. Specific examplesthereof include 2-acryloylethyl isocyanate and 2-methacryloylethylisocyanate. 2-Methacryloylethyl isocyanate is commercially availablefrom Showa Denko K.K. under the designation of “Karenz MOI” and thelike.

[0041] The reaction of the copolymer comprising the constituent unitsrepresented by formulae (1) to (5) with the (meth)acryloylalkylisocyanate compound may be carried out by adding dropwise the isocyanatecompound to a solution of the copolymer in the presence of a minoramount of a catalyst. Catalysts usable herein include dibutyltinlaurate. In the reaction, polymerization inhibitors, such asp-methoxyphenol, hydroquinone, naphthylamine, tert-butyl catechol, and2,3-di-tert-butyl p-cresol, may be used according to need.

[0042] The (meth)acryloylalkyl isocyanate compound is bonded to hydroxylgroups of the constituent units represented by formula (2) through aurethane bond, and bonded to a part of carboxyl groups in theconstituent units represented by formula (1) through an amido bond withthe evolution of carbon dioxide gas. A product of a reaction between thecopolymer comprising the constituent units represented by formulae (1)and (2) and the (meth)acryloylalkyl isocyanate compound is representedby formula (6). When the constituent units represented by formula (I)are unnecessary, the (meth)acryloylalkyl isocyanate compound is entirelybonded to the constituent units represented by formula (2). Theconstituent units represented by formula (3) are unreactive. Therefore,the description thereof will be omitted.

[0043] wherein R and R₁ each are as defined above in connection withformulae (1) to (4), R′ represents an alkylene group having 2 to 6carbon atoms, a₁+a₂ is a defined in formula (1), and b₁+b₂ is b definedin formula (2).

[0044] The rate of the reaction of the (meth)acryloylalkyl isocyanatecompound with hydroxyl groups in the constituent units represented byformula (2) is about 20 times higher than that of the reaction of the(meth)acryloylalkyl isocyanate compound with carboxyl groups in theconstituent units represented by formula (1). Therefore, the(meth)acryloyl group is mainly introduced into the constituent unitsrepresented by formula (2), and, in the constituent units represented byformula (1), most of the carboxyl groups remains unreacted even thoughthe (meth)acryloyl group is introduced into a part of the carboxylgroups.

[0045] In connection with formula (6), regarding the portion derivedfrom formula (2), the proportion of units with an index b₁ in thecopolymer resin may be 0 to 10% by mole, and the proportion of unitswith an index b2 in the copolymer resin may be 5 to 95% by mole,provided that total of the proportion of units with an index b₁ and theproportion of units with an index b₂ is 5 to 95% by mole, whileregarding the portion derived from formula (1), the proportion of unitswith an index a₁ in the copolymer resin may be 5 to 55% by mole, and theproportion of units with an index a₂ in the copolymer resin may be 0 to10% by mole, provided that the total of the proportion of units with anindex a₁ and the proportion of units with an index a₂ is 5 to 55% bymole. Thus, the amount of the (meth)acryloyl group introduced can beregulated.

[0046] The weight average molecular weight of the copolymer resinaccording to the present invention is generally 5,000 to 1,000,000,preferably 10,000 to 100,000, from the viewpoint of suitability for usein the formation of a protective layer for a color filter and, inaddition, of alkali solubility and photocurability. When the weightaverage molecular weight is smaller than 5,000, the developability isexcessively good. This makes it difficult to control pattern shapes atthe time of pattern-wise exposure. Even though patterns could be formed,a problem occurs such as a reduction in final coating thickness. On theother hand, when the weight average molecular weight exceeds 1,000,000,the viscosity of the copolymer resin in the form of a resist is so highthat the coatability is lowered. Further, in this case, thedevelopability is deteriorated. This makes it difficult to form sharppatterns.

[0047] The amount of the (meth)acryloyl group introduced is generally 5to 95% by mole, preferably 10 to 50% by mole. When the amount is lessthan 5% by mole, the photocurability is low and the effect of improvingcoating adhesion and resist properties is small.

[0048] The acid value of the epoxy-containing copolymer resin is 0 to400 mg KOH/g. The acid value may be determined by taking intoconsideration the relationship between the acid value of theepoxy-containing copolymer resin and that of the alkali-developablephotocurable copolymer resin described below. When the acid value isexcessively high, the stability of the epoxy-containing copolymer resinis unfavorably lowered. In the epoxy-containing copolymer resin, thehydroxyl group in the constituent units represented by formula (2) isnot always required to be left, and the hydroxyl value may be 0 to 200mg KOH/g. However, the hydroxyl group may be left to effectivelyregulate the solubility of the copolymer resin in the solvent.

[0049] Upon heating after the exposure and the development, theepoxy-containing copolymer resin according to the present invention isreacted with the acidic group remaining unreacted. Thus, alkaliresistance is imparted to the protective layer. As compared with theconventional phenol novolak epoxy resin or the like, theepoxy-containing copolymer resin has high miscibility with thealkali-developable photocurable copolymer resin by virtue of similarityof the structure, and, upon crosslinking at the time of heat curing, canbe brought to a strong pattern. Further, the epoxy-containing copolymerresin can form a pattern possessing excellent alkali resistance andwater resistance and thus can be brought to a photosensitive resincomposition possessing excellent sensitivity. The content of theepoxy-containing copolymer resin in the resin composition is 5 to 60% byweight on solid basis. When the content of the epoxy-containingcopolymer resin is less than 5% by weight, satisfactory alkaliresistance cannot be imparted to the protective layer. On the otherhand, when the content exceeds 60% by weight, the amount of the epoxyresin, which does not contribute to photocuring, is excessivelyincreased. This unfavorably deteriorates the storage stability anddevelopability of the resin composition.

[0050] Next, the alkali-developable photocurable copolymer resinaccording to the present invention will be described. In thealkali-developable photocurable copolymer resin, a copolymer resindescribed in Japanese Patent Application No. 99240/1998 is used. Thealkali-developable photocurable copolymer resin comprises the sameconstituent units as the epoxy-containing copolymer resin, except thatthe constituent units represented by formula (3) is omitted from theconstituent units represented by formulae (1) to (5). That is, thealkali-developable photocurable copolymer resin comprises 5 to 55% bymole of constituent units represented by formula (1) and 5 to 95% bymole of constituent units represented by formula (2), the constituentunits represented by formula (1) having been partially reacted, throughcarboxyl groups thereof, with a (meth)acryloylalkyl isocyanate compound,the constituent units represented by formula (2) having been partiallyreacted, through hydroxyl groups thereof, with a (meth)acryloylalkylisocyanate compound, said copolymer resin containing 5 to 95% by mole of(meth)acryloyl groups and having an acid value of 5 to 400 mg KOH/g anda weight average molecular weight of 5,000 to 1,000,000 as determinedusing polystyrene as a standard.

[0051] In the alkali-developable photocurable copolymer resin, theconstituent units represented by formula (1) are indispensable andfunction to render the copolymer resin alkali-soluble. Monomers for theconstituent units represented by formula (1) include those describedabove in connection with the epoxy-containing copolymer resin. Thecontent of the constituent units represented by formula (1) is 5 to 55%by mole, preferably 10 to 25% by mole.

[0052] The constituent units represented by formula (2) are the same asthose described above in connection with the epoxy-containing copolymerresin, and have been partially reacted through hydroxyl groups with a(meth)acryloylalkyl isocyanate compound to introduce (meth)acryloylgroups thereinto. The content of the constituent units represented byformula (2) is regulated according to the level of thephotopolymerizability required of the copolymer resin, and is 5 to 95%by mole, preferably 10 to 50% by mole.

[0053] The alkali-developable photocurable copolymer resin comprises theconstituent units represented by formulae (1) and (2). Other constituentunits usable for the alkali-developable photocurable copolymer resininclude constituent units represented by formulae (4) and (5) which arethe same as those described above in connection with theepoxy-containing copolymer resin. The content of the constituent unitsrepresented by formula (4) is 0 to 75% by mole, preferably 5 to 50% bymole. The content of the constituent units represented by formula (5) is0 to 75% by mole, preferably 5 to 50% by mole.

[0054] The alkali-developable photocurable copolymer resin may beproduced in the same manner as described above in connection with theepoxy-containing copolymer resin, and the same catalyst, polymerizationinitiator, and molecular weight regulator as used in the production ofthe epoxy-containing copolymer resin may be used in the production ofthe alkali-developable photocurable copolymer resin.

[0055] The weight average molecular weight of the alkali-developablecopolymer resin comprising the constituent units represented by formulae(1), (2), (4), and (5) as determined using polystyrene as a standard(hereinafter referred to simply as “weight average molecular weight” or“Mw”) may be the same as that of the epoxy-containing copolymer resin.The copolymer resin has an acid value of 5 to 400 mg KOH/g and ahydroxyl value of 5 to 400 mg KOH/g.

[0056] The alkali-developable photocurable copolymer resin may beproduced by reacting the copolymer resin comprising the constituentunits represented by formulae (1), (2), (4), and (5) with a(meth)acryloyl-containing isocyanate compound.

[0057] The (meth)acryloylalkyl isocyanate compound may be the same asdescribed above in connection with the epoxy-containing copolymer resin,and the (meth)acryloyl group may be introduced by the same reaction.

[0058] The weight average molecular weight of the alkali-developablephotocurable copolymer resin is 5,000 to 1,000,000, preferably 10,000 to100,000. When the weight average molecular weight is smaller than 5,000,the developability is excessively good. This makes it difficult tocontrol pattern shapes at the time of pattern-wise exposure. Even thoughpatterns could be formed, a problem occurs such as a reduction in finalcoating thickness. On the other hand, when the weight average molecularweight exceeds 1,000,000, the viscosity of the copolymer resin in theform of a resist is so high that the coatability is lowered. Further, inthis case, the developability is deteriorated. This makes it difficultto form sharp patterns.

[0059] The amount of the (meth)acryloyl group introduced is 5 to 95% bymole, preferably 10 to 50% by mole. When the amount is less than 5% bymole, the photocurability is low and the effect of improving coatingadhesion and resist properties is small.

[0060] The acid value of the alkali-developable, photocurable copolymerresin is 5 to 400 mg KOH/g, preferably 10 to 200 mg KOH/g. The acidvalue correlates with the alkali developability. Specifically, an acidvalue below the lower limit of the above range leads to problems such aspoor developability and poor adhesion to the substrate and the colorfilter resin. On the other hand, an acid value above the upper limit ofthe above range provides excessively good developability, posingproblems including the difficulty of regulating pattern shapes at thetime of pattern-wise exposure. In the copolymer resin, the hydroxylgroup in the constituent units represented by formula (2) is not alwaysrequired to be left, and the hydroxyl value may be 0 to 200 mg KOH/g.However, the hydroxyl group may be left to effectively regulate thesolubility of the copolymer resin in the solvent.

[0061] Alkali-developable photocurable copolymer resins suitable for thepresent invention will be exemplified. For all the copolymer resinsexemplified below, the constituent units represented by formula (1) arederived from 2-hydroxyethyl methacrylate (HEMA) as the monomer, and theconstituent units represented by formula (2) are derived from acrylicacid (AA) as the monomer. Further, the constituent units represented byformula (1) have been partially reacted, through carboxyl groupsthereof, with 2-methacryloylethyl isocyanate (Karenz MOI, manufacturedby Showa Denko K.K.), and the constituent units represented by formula(2) have been partially reacted, through hydroxyl groups thereof, with2-methacryloylethyl isocyanate (Karenz MOI, manufactured by Showa DenkoK.K.). The constituent units represented by formula (3) are derived fromstyrene (St) as the monomer, and the constituent units represented byformula (4) are derived from benzyl methacrylate (BZMA) as the monomer.

[0062] For the copolymer resins, the chemical composition (% by mole) isshown in Table 1, and the acryloyl group content (% by mole), the acidvalue (mg KOH/g), and the weight average molecular weight (Mw) asdetermined using polystyrene as the standard are shown in Table 2. TABLE1 Copolymer resin No. HEMA AA St BzMA (1) 18 30 37 15 (2) 20 20 35 25(3) 18 30 52 0 (4) 18 30 0 52

[0063] TABLE 2 Content of Copolymer resin No. Mw acryloyl group Acidvalue (1) 45,000 17.0 120 (2) 45,000 14.5 100 (3) 45,000 14.5 120 (4)45,000 14.5 120

[0064] The content of the alkali-developable, photocurable copolymerresin in the photosensitive resin composition according to the presentinvention is in an amount of 5 to 80% by weight, preferably 10 to 50% byweight, on a solid basis. When the content of the copolymer resin ismore than 80% by weight, the viscosity of the composition is excessivelyhigh, leading to lowered fluidity. This poses a problem of coatability.On the other hand, when the content of the copolymer is less than 5% byweight, the viscosity of the composition is excessively low, leading tounsatisfactory stability of a coating of the composition after coatingand drying. This poses problems such as deteriorated suitability forexposure and development.

[0065] Bifunctional or higher polyfunctional polymerizable acrylatemonomers usable herein include ethylene oxide (3 mol) adducts, ethyleneoxide (6 mol) adducts, propylene oxide (3 mol) adducts, and propyleneoxide (6 mol) adducts of dipentaerythritol hexaacrylate (DPHA),dipentaerythritol pentaacrylate (DPPA), pentaerythritol triacrylate(PETTA), trimethylolpropane triacrylate (TMPTA), and trimethylolpropanetriacrylate (TMPTA). The content of the bifunctional or higherpolyfunctional polymerizable acrylate monomer in the photosensitiveresin composition is generally 3 to 50% by weight, preferably 5 to 20%by weight, on a solid basis. When the bifunctional or higherpolyfunctional polymerizable acrylate monomer content is more than 50%by weight, the viscosity of the composition is excessively low, leadingto unsatisfactory stability of a coating of the composition aftercoating and drying. This poses problems such as deteriorated suitabilityfor exposure and development. On the other hand, a bifunctional orhigher polyfunctional polymerizable acrylate monomer content of lessthan 3% by weight poses a problem that unexposed portions cannot befully removed in the development.

[0066] Initiators usable herein include: radical polymerizationinitiators; and photo-induced acid generators which can generate acidsupon exposure to light (particularly light with wavelengths of 190 to410 nm). Radical polymerization initiators include2=methyl-1-[(4-methylthio)phenyl]-2-morpholinopropanone-1,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2,2′-bis(o-chlorophenyl)-4,5,4′,5′-tetraphenyl-1,2′-biimidazole,2,4-diethylthioxanthone, and 4,4-bisdiethylaminobenzophenone. The amountof the radical polymerization initiator used is generally 0.1 to 100parts by weight, preferably 0.5 to 50 parts by weight, based on 100parts by weight of the copolymer resin. When the amount of the radicalpolymerization initiator used is less than 0.1 part by weight, aphotocuring reaction does not proceed. This results in lowered thicknessof the final coating, heating resistance, chemical resistance or otherproperties. On the other hand, when the amount of the radicalpolymerization initiator used exceeds 100 parts by weight, thesolubility thereof in the copolymer resin is saturated. This causes theprecipitation of crystals of the initiator at the time of spin coatingor leveling of the coating. This in turn makes it impossible to maintainthe homogeneity of the coating in its surface and roughens the coating.

[0067] Photo-induced acid generators include the following compounds.

[0068] (1) Trichloromethyl-s-triazines:tris(2,4,6-trichloromethyl)-s-triazine,2-phenyl-bis(4,6-trichloromethyl)-s-triazine,2-(4-chlorophenyl)-bis(4,6-trichloromethyl)-s-triazine,2-(3-chlorophenyl)-bis(4,6-tri-chloromethyl)-s-triazine,2-(2-chlorophenyl)-bis-(4,6-trichloromethyl)-s-triazine,2-(4-methoxyphenyl)-bis (4,6-trichloromethyl)-s-triazine,2-(3-methoxyphenyl)-bis(4,6-trichloromethyl)-s-triazine,2-methoxyphenyl)-bis (4,6-trichloromethyl)-s-triazine,2-(4-methylthiophenyl)-bis(4,6-trichloromethyl)-s-triazine,2-(3-methylthiophenyl)-bis(4,6-trichloromethyl)-s-triazine,2-(2-methylthiophenyl)-bis(4,6-trichloromethyl)-s-triazine,2-(4-methoxynaphthyl)-bis(4,6-trichloromethyl)-s-triazine,2-(3-methoxynaphthyl)-bis(4,6-trichloromethyl)-5-triazine,2-(2-methoxynaphthyl)-bis-(4,6-trichloromethyl)-s-triazine,2-(4-methoxy-β-styryl)-bis(4,6-trichloromethyl)-s-triazine,2-(3-methoxy-β-styryl)-bis(4,6-trichloromethyl)-s-triazine,2-(2-methoxy-β-styryl)-bis(4,6-trichloromethyl)-s-triazine,2-(4-methylthio- -styryl)-bis(4,6-trichloromethyl)-s-triazine,2-(3-methylthio-β-styryl)-bis(4,6-trichloromethyl)-s-triazine,2-(2-methylthio-β-styryl)-bis(4,6-trichloromethyl)-s-triazine and thelike.

[0069] (2) Diaryliodonium salts: diphenyliodonium tetrafluoroborate,diphenyliodonium hexafluorophosphonate, diphenyliodoniumhexafluoroarsenate, diphenyliodonium hexafluoromethanesulfonate,diphenyliodonium trifluoroacetate, diphenyliodonium p-toluenesulfonate,4-methoxyphenylphenyliodonium tetrafluoroborate,4-methoxyphenylphenyliodonium hexafluorophosphonate,4-methoxyphenylphenyliodonium hexafluoroarsenate,4-methoxyphenylphenyliodonium trifluoromethanesulfonate,4-methoxyphenylphenyliodonium trifluoroacetate,4-methoxyphenylphenyliodonium p-toluenesulfonate,bis(4-tert-butylphenyl)iodonium tetrafluoroborate,bis(4-tert-butylphenyl)iodonium hexafluorophosphonate,his(4-tert-butylphenyl)iodonium hexafluoroarsenate,bis(4-tert-butylphenyl)iodonium hexafluoromethanesulfonate,bis(4-tert-butylphenyl)iodonium trifluoroacetate,bis(4-tert-butylphenyl)iodonium p-toluenesulfonate and the like.

[0070] (3) Triarylsulfonium salts: triphenylsulfonium tetrafluoroborate,triphenylsulfonium hexafluoro-phosphonate, triphenylsulfoniumhexafluoroarsenate, triphenylsulfonium hexafluoromethanesulfonate,triphenylsulfonium trifluoroacetate, triphenylsulfoniump-toluenesulfonate, 4-methoxydiphenylsulfonium tetrafluoroborate,4-methoxydiphenylsulfonium hexafluorophosphonate,4-methoxydiphenylsulfonium hexafluoroarsenate,4-methoxydiphenylsulfonium hexafluoromethanesulfonate,4-methoxydiphenylsulfonium trifluoroacetate, 4-methoxydiphenylsulfoniump-toluenesulfonate, 4-phenylthiophenyldiphenyl tetrafluoroborate,4-phenylthiophenyldiphenyl hexafluorophosphonate,4-phenylthiophenyldiphenyl hexafluoroarsenate,4-phenylthiophenyldiphenyl hexafluoromethanesulfonate,4-phenylthiophenyldiphenyl trifluoroacetate, 4-phenylthiophenyldiphenylp-toluenesulfonate and the like.

[0071] Among these compounds, preferred trichloromethyl-s-triazinesinclude 2-(3-chlorophenyl)-bis(4,6-trichloromethyl)-s-triazine,2-(4-methoxyphenyl)-bis(4,6-tri-chloromethyl)-s-triazine,2-(4-methylthiophenyl)-bis-(4,6-trichloromethyl)-s-triazine,2-(4-methoxy- β-styryl)-bis(4,6-trichloromethyl)-s-triazine, and2-(4-methoxynaphthyl)-bis(4,6-trichloromethyl)-s-triazine.

[0072] Preferred diaryliodonium salts include diphenyliodoniumtrifluoroacetate, 4-methoxy-phenylphenyliodoniumtrifluoromethanesulfonate, 4-methoxyphenylphenyliodoniumtrifluorophosphonate, and 4-methoxyphenylphenyliodoniumtrifluoroacetate.

[0073] Preferred triarylsulfonium salts include triphenylsulfoniumtrifluoromethanesulfonate, triphenyl-sulfonium trifluoroacetate,4-methoxydiphenylsulfonium tetrafluoromethanesulfonate,4-methoxydiphenylsulfonium tetrafluoroacetate, and4-phenylthiophenyldiphenyl-sulfonium trifluoroacetate.

[0074] The amount of the photo-induced acid generator added is generally0.001 to 30 parts by weight, preferably 0.01 to 10 parts by weight,based on 100 parts by weight of the copolymer resin. When the amount ofthe photo-induced acid generator added is less than 0.001 part byweight, the amount of the acid generated upon the exposure of thephoto-induced acid generator to light is too small to progress aphotocuring reaction or crosslinking. This is likely to cause loweredthickness of the final coating, heating resistance, chemical resistanceor other properties. On the other hand, when the amount of thephoto-induced acid generator added exceeds 30 parts by weight, thesolubility thereof in the composition (containing a solvent) issaturated. This is likely to cause the precipitation of crystals on thecoating or dimerization or trimerization of the photo-induced acidgenerator which lowers the light absorption efficiency and consequentlylowers the sensitivity. Photo-induced acid generators may be used as amixture of two or more.

[0075] Commercially available photo-induced acid generators includethose manufactured by Midori Kagaku Co., Ltd., for example, triazinesincluding TAZ-100, TAZ-101, TAZ-102, TAZ-104, TAZ-106, TAZ-107, TAZ-110,TAZ-111, TAZ-113, TAZ-114, TAZ-118, TAZ-119, and TAZ-120 and oniumsalts, for example, triphenylsulfonium salts including TPS-102, TPS-103,TPS-105, MDS-103, MDS-105, MDS-305, BDS-105, DTS-102, DTS-103, MAT-103,MAT-105, NDS-103, and NDS-105.

[0076] Silane coupling agents may be added to improve the adhesion ofthe color filter layer to the substrate glass. Silane coupling agentsusable herein include vinylsilane, acrylsilane, epoxysilane, andaminosilane. More specifically, examples of vinylsilanes usable hereininclude vinyltrichlorosilane, vinyltris(β-methoxyethoxy)silane,vinyltriethoxysilane, and vinyltrimethoxysilane. Examples ofacrylsilanes usable herein include γ-methacryloxypropyltrimethoxysilaneand γ-methacryloxypropylmethyldimethoxysilane. Examples of epoxysilanesusable herein include β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-glycidoxypropyltrimethoxysilane, andγ-glycidoxypropylmethyldiethoxysilane. Examples of aminosilanes usableherein include N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane,N-β-(aminoethyl)-γ-amino-propylmethylditrimethoxysilane,γ-aminopropyl-triethoxysilane, andN-phenyl-γ-aminopropyl-trimethoxysilane. Examples of other silanecoupling agents usable herein include γ-mercaptopropyl-trimethoxysilane,γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldimethoxysilane,γ-chloropropylmethyl-dimethoxysiliane,and-γ-chloropropylmethyldiethoxysilane.

[0077] In order to improve the suitability for coating, a surfactant maybe added, and examples of surfactants usable herein includefluorosurfactants and silicone surfactants.

[0078] According to the photosensitive resin composition of the presentinvention, for example, diethylene glycol dimethyl ether, 3-methoxybutylacetate, propylene glycol monomethyl ether acetate, and3-methyl-3-methoxybutanol may be used as a solvent to give aconcentration of 5 to 50% by weight on a solid basis.

[0079] According to the photosensitive resin composition of the presentinvention, an alkali-developable photocurable copolymer resin havingcontrolled alkali solubility and curability is used in combination withan epoxy-containing copolymer resin having excellent miscibility withthe resin. Therefore, the photosensitive resin composition of thepresent invention possesses excellent hot pure water resistance, solventresistance, heat resistance, alkali resistance, sensitivity, and pencilhardness.

[0080] Next, the color filter of the present invention will bedescribed. FIG. 1 is a schematic diagram showing the construction of oneembodiment of the color filter according to the present invention. InFIG. 1, a color filter 1 according to the present invention comprises: atransparent substrate 2; a colored layer 3 and a black matrix 4 eachhaving a predetermined pattern provided on the transparent substrate 2;a protective layer 5 provided so as to cover the colored layer 3; and atransparent electrode 6 provided on the protective layer 5, for aliquid-crystal drive.

[0081] In the color filter 1, nonflexible rigid materials, such asquartz glass, Pyrex glass, and synthetic quartz plates, or flexiblematerials, such as transparent resin films and resin plates for opticalpurposes, may be used for constituting the transparent substrate 2.Among them, Glass 7059 manufactured by Corning has a low coefficient ofthermal expansion, has excellent dimensional stability and workabilityin heat treatment at high temperatures, and, because of an alkali-freeglass, is particularly suitable for color filters used in colorliquid-crystal displays.

[0082] The colored layer 3 in the color filter 1 has a red pattern 3R, agreen pattern 3G, and a blue pattern 3B arranged in a desired form suchas mosaic, stripe, triangular, or four-pixel placement. The black matrix4 is provided between adjacent color patterns and the outside of thecolored layer 3 forming region in its predetermined portion.

[0083] The colored layer 3 may be formed by any method, for example, adyeing method which comprises coating a dyeing substrate, exposing thedyeing substrate through a photomask, developing the exposed dyeingsubstrate to form a pattern, and dyeing the pattern, a pigmentdispersion method which comprises previously dispersing a color pigmentin a photosensitive resist, exposing the resist through a photomask, anddeveloping the exposed resist, a printing method wherein each color isprinted using printing inks, or an electrodeposition method whichcomprises previously forming a transparent conductive layer on atransparent substrate, forming a positive-working resist layer on thetransparent conductive layer, exposing the resist layer through aphotomask, developing the exposed resist layer to expose predeterminedportions of the transparent conductive layer, immersing the transparentsubstrate in an electrodeposition liquid, and, in this state, energizingthe transparent conductive layer to perform electrodeposition, therebyforming a colored layer.

[0084] The black matrix 4 also may be formed by any one of the dyeingmethod, pigment dispersion method, printing method, andelectrodeposition method. Further, chromium vapor deposition or the likemay be used for the formation of the black matrix 4.

[0085] The protective layer may be formed by coating the photosensitiveresin composition of the present invention onto the transparentsubstrate, with the colored layer and the black matrix formed thereon,by spin coating, roller coating, spray coating, printing or the like toa thickness of 0.5 to 20 μm, preferably 1 to 8 μm, on a dry basis,exposing the coating through a predetermined photomask, and thendeveloping the exposed coating. When spin coating is used, the number ofrevolutions of the spin coater is preferably 500 to 1500 rpm.

[0086] The exposure of the coating is carried out by applyingultraviolet light through a photomask. After the exposure, alkalidevelopment is carried out, followed by heat treatment (post-baking).Thus, the protective layer is formed. The protective layer 5 has a filmstrength of not less than 4H in terms of pencil hardness after immersionof the protective layer in an 1% aqueous sodium hydroxide solution(solution temperature=25° C.) for 24 hr. Further, after the immersion inthe alkali solution, the protective layer is not separated. That is, theprotective layer 5 has very high alkali resistance.

[0087] After the exposure and the development with an alkali, unreactedacid groups are present in the photosensitive resin composition.According to the present invention, however, since the epoxy resincontained in the photosensitive resin composition is reacted with theresidual acid groups upon heat treatment, any acid group reactive withan alkali is absent in the formed protective layer. Therefore, theprotective layer has excellent alkali resistance.

[0088] Heat treatment (post-baking) after the completion of the exposureof the coating of the photosensitive resin composition and the alkalidevelopment may be generally carried out under conditions of 120 to 250°C. and about 5 to 90 min. This heat treatment permits the epoxy resincontained in the photosensitive resin composition to be reacted with theremaining acid groups.

[0089] The transparent electrode may be provided on the protective layerby a conventional film forming method, such as sputtering, vacuumdeposition, or CVD, using indium tin oxide (ITO), zinc oxide (ZnO), tinoxide (SnO), or an alloy thereof and optionally performing etching usinga photoresist to form a predetermined pattern. The thickness of thetransparent electrode is about 20 to 500 nm, preferably about 100 to 300nm.

[0090] The following examples further illustrate the present invention.

Synthesis of Epoxy-containing Copolymer Resin {circumflex over (1)}

[0091] The following composition was provided. Methyl methacrylate 571 g2-Hydroxyethyl methacrylate 163 g Glycidyl methacrylate  81 g

[0092] This composition, together with 5 g of azobisisobutyronitrile,was dissolved in 650 g of 3-methoxybutyl acetate. The solution was thenadded dropwise to a polymerizer containing 1000 g of 3-methoxybutylacetate at 100° C. over a period of 6 hr. Thus, polymerization wascarried out to prepare a polymer solution.

[0093] The polymer solution had a solid content of 33% by weight and aviscosity of 31.8 mPa•-s (25° C. , Brookfield viscometer). The polymerhad a weight average molecular weight of 10,000 as determined usingpolystyrene as a standard.

[0094] The copolymer thus obtained comprised 75.8% by mole of methylmethacrylate units, 16.7% by mole of 2-hydroxyethyl methacrylate units,and 7.5% by mole of glycidyl methacrylate units.

[0095] A mixture having the following composition was added dropwise tothe polymer solution over a period of 5 hr. 2-Methacryloylethylisocyanate  270 g Dibutyltin laurate   1 g 3-Methoxybutyl acetate 2230 g

[0096] The progress of the reaction was monitored by IR (an infraredabsorption spectrum), and the reaction was continued until the peakattributable to the isocyanate group at 2200 cm⁻¹ had disappeared.

[0097] The reaction solution thus obtained had a solid content of 22% byweight and a viscosity of 20 mPa•s (25° C., Brookfield viscometer). Thepolymer had a weight average molecular weight of 11,000 as determinedusing polystyrene as a standard.

Synthesis of Epoxy-containing Copolymer Resin {circumflex over (2)}

[0098] The following composition was provided. Benzyl methacrylate 204 gStyrene 286 g 2-Hydroxyethyl methacrylate 163 g Glycidyl methacrylate163 g

[0099] This composition, together with 5 g of azobisisobutyronitrile,was dissolved in 650 g of 3-methoxybutyl acetate. The solution was thenadded dropwise to a polymerizer containing 1000 g of 3-methoxybutylacetate at 100° C. over a period of 6 hr. Thus, polymerization wascarried out to prepare a polymer solution.

[0100] The polymer solution had a solid content of 33% by weight and aviscosity of 41.3 mPa•s (25° C., Brookfield viscometer). The polymer hada weight average molecular weight of 11,000 as determined usingpolystyrene as a standard.

[0101] The copolymer thus obtained comprised 18.3% by mole of benzylmethacrylate units, 43.6% by mole of styrene units, 19.9% by mole of2-hydroxyethyl methacrylate units, and 18.2% by mole of glycidylmethacrylate units.

[0102] A mixture having the following composition was added dropwise tothe polymer solution over a period of 5 hr. 2-Methacryloylethylisocyanate  270 g Dibutyltin laurate   1 g 3-Methoxybutyl acetate 2230 g

[0103] The progress of the reaction was monitored by IR (an infraredabsorption spectrum), and the reaction was continued until the peakattributable to the isocyanate group at 2200 cm⁻¹ had disappeared.

[0104] The reaction solution thus obtained had a solid content of 21% byweight and a viscosity of 25 mPa•s (25° C., Brookfield viscometer). Thepolymer had a weight average molecular weight of 12,000 as determinedusing polystyrene as a standard.

Synthesis of Epoxy-containing Copolymer Resin {circumflex over (3)}

[0105] The following composition was provided. Methyl methacrylate 489 g2-Hydroxyethyl methacrylate 163 g Oxetane methacrylate (OXE-30, 163 gmanufactured by Osaka Organic Chemical Industry Ltd.)

[0106] This composition, together with 5 g of azobisisobutyronitrile,was dissolved in 650 g of 3-methoxybutyl acetate. The solution was thenadded dropwise to a polymerizer containing 1000 g of 3-methoxybutylacetate at 100° C. over a period of 6 hr. Thus, polymerization wascarried out to prepare a polymer solution.

[0107] The polymer solution had a solid content of 33% by weight and aviscosity of 40.3 mPa•s (25° C. , Brookfield viscometer). The polymerhad a weight average molecular weight of 10,000 as determined usingpolystyrene as a standard.

[0108] The copolymer thus obtained comprised 69.5% by mole of methylmethacrylate units, 17.9% by mole of 2-hydroxyethyl methacrylate units,and 12.6% by mole of oxetane methacrylate units.

[0109] A mixture having the following composition was added dropwise tothe polymer solution over a period of 5 hr. 2-Methacryloylethylisocyanate  270 g Dibutyltin laurate   1 g 3-Methoxybutyl acetate 2230 g

[0110] The progress of the reaction was monitored by IR (an infraredabsorption spectrum), and the reaction was continued until the peakattributable to the isocyanate group at 2200 cm⁻¹ had disappeared.

[0111] The reaction solution thus obtained had a solid content of 21% byweight and a viscosity of 27 mPa•s (25° C., Brookfield viscometer). Thepolymer had a weight average molecular weight of 12,000 as determinedusing polystyrene as a standard.

Synthesis of Epoxy-containing Copolymer Resin {circumflex over (4)}

[0112] The following composition was provided. Methyl methacrylate 530 g2-Hydroxyethyl methacrylate 163 g Methacrylic acid  41 g Oxetanemethacrylate (OXE-30, 184 g manufactured by Osaka Organic ChemicalIndustry Ltd.)

[0113] This composition, together with 5 g of azobisisobutyronitrile,was dissolved in 800 g of 3-methoxybutyl acetate. The solution was thenadded dropwise to a polymerizer containing 1000 g of 3-methoxybutylacetate at 80° C. over a period of 5 hr. Thus, polymerization wascarried out to prepare a polymer solution.

[0114] The polymer solution had a solid content of 34% by weight and aviscosity of 34.7 mPa•s (25° C., Brookfield viscometer). The polymer hada weight average molecular weight of 8,600 as determined usingpolystyrene as a standard.

[0115] The copolymer thus obtained comprised 70.9% by mole of methylmethacrylate units, 16.8% by mole of 2-hydroxyethyl methacrylate units,6.4% by mole of methacrylic acid units, and 5.9% by mole of oxetanemethacrylate units.

[0116] A mixture having the following composition was added dropwise tothe polymer solution over a period of 5 hr. 2-Methacryloylethylisocyanate  270 g Dibutyltin laurate   1 g 3-Methoxybutyl acetate 2230 g

[0117] The progress of the reaction was monitored by IR (an infraredabsorption spectrum), and the reaction was continued until the peakattributable to the isocyanate group at 2200 cm⁻¹ had disappeared.

[0118] The reaction solution thus obtained had a solid content of 21% byweight and a viscosity of 24 mPa•s (25° C., Brookfield viscometer). Thepolymer had an acid value of 23.2 mg KOH/g, and a weight averagemolecular weight of 9,300 as determined using polystyrene as a standard.

Synthesis of Alkali-developable Photocurable Copolymer Resin (1) Shownin Table 1

[0119] The following composition was provided. Benzyl methacrylate 264 gStyrene 385 g Acrylic acid 216 g 2-Hydroxyethyl methacrylate 234 g

[0120] This composition, together with 5 g of azobisisobutyronitrile,was dissolved in 650 g of 3-methoxybutyl acetate. The solution was thenadded dropwise to a polymerizer containing 1,000 g of 3-methoxybutylacetate at 100° C. over a period of 6 hr. Thus, polymerization wascarried out to prepare a polymer solution.

[0121] The polymer solution had a solid content of 40% by weight and aviscosity of 1,050 mPa•s (30° C., Brookfield viscometer). The polymerhad an acid value of 152 mg KOH/g, a hydroxyl value of 90 mg KOH/g, anda weight average molecular weight of 37,000 as determined usingpolystyrene as a standard.

[0122] The copolymer thus obtained comprised 15% by mole of styreneunits, 37% by mole of benzyl methacrylate units, 30% by mole of acrylicacid units, and 18% by mole of 2-hydroxyethyl methacrylate units.

[0123] A mixture having the following composition was added dropwise tothe polymer solution over a period of 5 hr. 2-Methacryloylethylisocyanate  270 g Dibutyltin laurate   1 g 3-Methoxybutyl acetate 2230 g

[0124] The progress of the reaction was monitored by IR (an infraredabsorption spectrum), and the reaction was continued until the peakattributable to the isocyanate group at 2200 cm⁻¹ had disappeared.

[0125] The reaction solution thus obtained had a solid content of 26% byweight and a viscosity of 500 mPa•s (30° C., Brookfield viscometer). Thepolymer had an acid value of 120 mg KOH/g, a hydroxyl value of 5 mgKOH/g, and a weight average molecular weight of 45,000 as determinedusing polystyrene as a standard and contained 17% by mole of(meth)acryloyl groups.

EXAMPLE 1

[0126] A red photosensitive resin having the following composition wasspin coated on a 1.1 mm-thick glass substrate (AL material, manufacturedby Asahi Glass Co., Ltd.) to a coating thickness of 1.5 μm. The coatedsubstrate was dried for 30 min in an oven of 70° C. Next, the coatedsurface was exposed to light from a mercury lamp through a photomaskhaving a predetermined pattern, followed by spray development with waterfor one min to form a red relief pattern in regions where red pixels areto be formed. Thereafter, curing treatment was carried out at 15° C. for30 min.

[0127] Next, the same procedure as used in the formation of the redrelief pattern was repeated, except that a green photosensitive resinhaving the following composition was used. Thus, a green relief patternwas formed in regions where green pixels are to be formed.

[0128] The same procedure as used in the formation of the red reliefpattern was then repeated, except that a blue photosensitive resinhaving the following composition was used. Thus, a blue relief patternwas formed in regions where blue pixels are to be formed. Thus, coloredlayers of three colors, red (R), green (G), and blue (B) were prepared.(Composition of red photosensitive resin) Pyrazolone Red (red pigment)10 pts. wt. Polyvinyl alcohol/5% stilbazolium  5 pts. wt. quinolium(photosensitive resin) Water 85 pts. wt. (Composition of greenphotosensitive resin) Lionol Green 2Y-301 (green pigment)  9 pts. wt.Polyvinyl alcohol/5% stilbazolium  5 pts. wt. quinolium (photosensitiveresin) Water 86 pts. wt. (Composition of blue photosensitive resin)Fastogen Blue (blue pigment)  3 pts. wt. Polyvinyl alcohol/5%stilbazolium  5 pts. wt. quinolium (photosensitive resin) Water 92 pts.wt.

[0129] A photosensitive resin composition prepared by the followingmethod was spin coated onto the glass substrate, with the colored layersformed thereon, to a coating thickness of 1.2 μm on a dry basis.

Preparation of Photosensitive Resin Composition A

[0130] The following compounds were provided. Alkali-developablephotocurable copolymer  8.1 pts. wt. resin (1) synthesized above (solidcontent 26 wt %) Dipentaerythritol pentaacrylate  6.3 pts. wt. (SR 399,manufactured by Sartomer) Epoxy-containing copolymer resin {circle over(1)} 10.8 pts. wt. synthesized above (on a solid basis)2-Methyl-1-[(4-methylthio)phenyl]-2-  1.2 pts. wt. morpholinopropanone-12,2′-Bis(o-chlorophenyl)-4,5,4′,5′-  0.9 pt. wt.tetraphenyl-1,2′-biimidazole Triazine (TAZ 110, manufactured by  0.3 pt.wt. Midori Kagaku Co., Ltd. Diethylene glycol dimethyl ether 34.6 pts.wt. 3-Methoxybutyl acetate 37.0 pts. wt.

[0131] They were mixed together at room temperature with stirring toprepare a photosensitive resin composition A of the present invention.

Step of Exposure and Development

[0132] The coatings of the photosensitive resin compositions were fullyair dried, and then prebaked on a hot plate at 80° C. for 5 min.Thereafter, a photomask was disposed at a position 100 μm distant fromthe coating of the photosensitive resin composition. Ultraviolet lightwas applied by a proximity aligner from a 2.0 kW ultrahigh-pressuremercury lamp at an exposure of 100 mJ/cm² only to regions correspondingto colored layer-forming regions. The exposed assembly was then immersedin a 0.05% aqueous potassium hydroxide solution (liquid temperature 23°C.) for one min to perform alkali development. Thus, only uncuredportions in the coating of the photosensitive resin composition wereremoved.

[0133] Thereafter, the assembly was allowed to stand in a clean oven inan atmosphere of 180° C. for 30 min to perform final curing, therebyforming a transparent protective layer. The thickness of the transparentprotective layer after the final curing was about 1.5 μm.

EXAMPLE 2

[0134] A photosensitive resin composition B was prepared in the samemanner as in Example 1, except that the epoxy-containing copolymer resin{circumflex over (2)} was used instead of the epoxy-containing copolymerresin {circumflex over (1)} prepared above. A color filter was thenprepared in the same manner as in Example 1, except that thephotosensitive resin composition B prepared just above was used.

EXAMPLE 3

[0135] A photosensitive resin composition C was prepared in the samemanner as in Example 1, except that the epoxy-containing copolymer resin{circumflex over (3)} was used instead of the epoxy-containing copolymerresin {circumflex over (1)} prepared above. A color filter was thenprepared in the same manner as in Example 1, except that thephotosensitive resin composition C prepared just above was used.

Comparative Example 1

[0136] A color filter was prepared in the same manner as in Example 1,except that the following photosensitive resin composition D was usedinstead of the photosensitive resin composition in Example 1.

[0137] The following compounds were provided. Alkali-developablephotocurable copolymer 10.0 pts. wt. resin (1) synthesized above (solidcontent 26 wt %) Dipentaerythritol pentaacrylate 15.2 pts. wt. (SR 399,manufactured by Sartomer) 2-Methyl-1-[(4-methylthio)phenyl]-2-  1.2 pts.wt. morpholinopropanone-1 2,2′-Bis(o-chlorophenyl)-4,5,4′,5′-  0.9 pt.wt. tetraphenyl-1,2′-biimidazole Triazine (TAZ 110, manufactured by  0.3pt. wt. Midori Kagaku Co., Ltd. Diethylene glycol dimethyl ether 34.6pts. wt. 3-Methoxybutyl acetate 37.0 pts. wt.

[0138] They were mixed together at room temperature with stirring.

Comparative Example 2

[0139] A color filter was prepared in the same manner as in Example 1,except that the following photosensitive resin composition E was usedinstead of the photosensitive resin composition in Example 1.

[0140] The following compounds were provided. Alkali-developablephotocurable copolymer  8.1 pts. wt. resin (1) synthesized above (solidcontent 26 wt %) Dipentaerythritol pentaacrylate  6.3 pts. wt. (SR 399,manufactured by Sartomer) Bisphenol A type epoxy resin 10.8 pts. wt. (asa solid content) 2-Methyl-1-[(4-methylthio)phenyl]-2-  1.2 pts. wt.morpholinopropanone-1 2,2′-Bis(o-chlorophenyl)-4,5,4′,5′-  0.9 pt. wt.tetraphenyl-1,2′-biimidazole Diethylene glycol dimethyl ether 34.6 pts.wt. 3-Methoxybutyl acetate 37.0 pts. wt.

[0141] They were mixed together at room temperature with stirring.

[0142] The photosensitive resin compositions A to E were coated directlyon a 1.1 mm-thick glass substrate (AL material, manufactured by AsahiGlass Co., Ltd.) in the same manner as described above, and the coatingswere treated in the same manner as described above to form protectivelayers. The protective layers on the color filters and the protectivelayers on the glass plate were evaluated for hot pure water resistance,solvent resistance, heat resistance, alkali resistance, sensitivity, andpencil hardness under the following conditions.

Hot Pure Water Resistance

[0143] The samples were immersed in pure water of 80° C. for one hr, anda cross-cut tape peel test was then carried out.

Solvent Resistance

[0144] The samples were immersed in N-methylpyrrolidone of 40° C. forone hr, and a cross-cut tape peel test was then carried out.

Heat Resistance

[0145] The samples were allowed to stand in a clean oven of 250° C. forone hr, and a cross-cut tape peel test was then carried out.

Alkali Resistance

[0146] The samples were immersed in a 1% aqueous sodium hydroxidesolution of 23° C. for 24 hr, and a cross-cut tape peel test was thencarried out.

Sensitivity

[0147] The sensitivity was evaluated in terms of exposure which canresolve a 30-μm line-and-space pattern which can withstand development.

Pencil Hardness

[0148] The pencil hardness was measured according to the testing method8.4.1 in a pencil scratch test specified in JIS K 5400-1990.

[0149] The cross-cut tape peel test in the evaluation for the hot purewater resistance, the solvent resistance, the heat resistance, and thealkali resistance was carried out by the following method according toJIS K 5400-1990 8.5.

[0150] On a substantially middle portion of a test piece were provided11 parallel cut flaw lines at clearance intervals of 1 mm in each ofvertical and lateral directions of the test piece in such a manner thatthe cut flaw lines in the vertical direction were orthogonal to the cutflaw lines in the lateral direction to form 100 cross cuts in one cm².In the provision of the cut flaw lines, a cutter guide or the like wasused, and, while the knife edge of a cutter knife was kept at a definiteangle in the range of 35 to 45 degrees to the surface of the coating,the cutter knife was drawn so as to reach through the coating to thesubstrate of the test piece at an equal speed of 0.5 sec per cut flowline. A pressure-sensitive adhesive tape was applied to the test piecewith cut flaws provided therein, and then separated from the test piece.The state of cross-cut flaws was observed. The results were evaluatedaccording to the following criteria.

Evaluation Criteria

[0151] 10: Each cut flaw was fine, both sides of each cut flaw weresmooth, and the intersecting point of cut flaws and each square cut werefree from peeling.

[0152] 8: Slight peeling was observed at the intersecting point of cutflaws, each square cut was free from peeling, and the defect part waswithin 5% of the total square area.

[0153] 6: Peeling was observed at both sides and intersecting point ofcut flaws, and the defect part was 5 to 15% of the total square area.

[0154] 4: The width of peeling caused by cut flaw was large, and thedefect part was 15 to 35% of the total square area.

[0155] 2: The width of peeling caused by cut flaw was broader than 4points, and the defect part was 35 to 65% of the total square area.

[0156] 0: The peel area was not less than 65% of the total square area.TABLE 3 Hot pure water Solvent Heat Alkali Pencil Sensitivity, Resinresistance resistance resistance resistance hardness mJ/cm² Protective A10 10 10 8 3H 75 layer on glass B 10 10 10 8 3H 75 substrate C 10 10 108 3H 75 D 0 4 6 0 H 75 E 6 6 6 6 2H 150 Protective A 8 8 8 — — — layeron color B 8 8 8 — — — filter C 8 8 8 — — — D 0 4 6 — — — E 4 6 6 — — —

What is claimed is:
 1. An epoxy-containing copolymer resin comprising 0to 55% by mole of constituent units represented by formula (1), 5 to 95%by mole of constituent units represented by formula (2), and 5 to 95% bymole of constituent units represented by formula (3), the constituentunits represented by formula (1) having been partially reacted, throughcarboxyl groups thereof, with a (meth)acryloylalkyl isocyanate compound,the constituent units represented by formula (2) having been partiallyreacted, through hydroxyl groups thereof, with a (meth)acryloylalkylisocyanate compound, said copolymer resin containing 5 to 95% by mole of(meth)acryloyl groups and having an acid value of 0 to 400 mg KOH/g anda weight average molecular weight of 5,000 to 1,000,000 as determinedusing polystyrene as a standard:

wherein R represents hydrogen or an alkyl group having 1 to 5 carbonatoms; R₁ represents an alkylene group having 2 to 4 carbon atoms; R₂represents an alkylene group having 1 to 4 carbon atoms; Z represents a1,2-epoxy, 1,3-epoxy, or 1,4-epoxy group; and a, b, and c are integersrespectively corresponding to said molar percentages.
 2. The copolymerresin according to claim 1, wherein the copolymer resin furthercomprises 0 to 75% by mole of constituent units represented by formula(4) and 0 to 75% by mole of constituent units represented by formula(5):

wherein R represents hydrogen or an alkyl group having 1 to 5 carbonatoms, R₂ represents an aromatic carbon ring, R₃ represents an alkyl oraralkyl group, and d and e are integers corresponding respectively tocontents in terms of % by mole of the constituent units.
 3. Aphotosensitive resin composition comprising: an alkali-developablephotocurable copolymer resin; an epoxy-containing copolymer resin; abifunctional or higher polyfunctional photopolymerizable acrylatemonomer; and an initiator, said alkali-developable photocurablecopolymer resin comprising 5 to 55% by mole of constituent unitsrepresented by formula (1) and 5 to 95% by mole of constituent unitsrepresented by formula (2), the constituent units represented by formula(1) having been partially reacted, through carboxyl groups thereof, witha (meth)acryloylalkyl isocyanate compound, the constituent unitsrepresented by formula (2) having been partially reacted, throughhydroxyl groups thereof, with a (meth)acryloylalkyl isocyanate compound,said copolymer resin containing 5 to 95% by mole of (meth)acryloylgroups and having an acid value of 5 to 400 mg KOH/g and a weightaverage molecular weight of 5,000 to 1,000,000 as determined usingpolystyrene as a standard, said epoxy-containing copolymer resincomprising 0 to 55% by mole of constituent units represented by formula(1), 5 to 95% by mole of constituent units represented by formula (2),and 5 to 95% by mole of constituent units represented by formula (3),the constituent units represented by formula (1) having been partiallyreacted, through carboxyl groups thereof, with a (meth)acryloylalkylisocyanate compound, the constituent units represented by formula (2)having been partially reacted, through hydroxyl groups thereof, with a(meth)acryloylalkyl isocyanate compound, said copolymer resin containing5 to 95% by mole of (meth)acryloyl groups and having an acid value of 0to 400 mg KOH/g and a weight average molecular weight of 5,000 to1,000,000 as determined using polystyrene as a standard:

wherein R represents hydrogen or an alkyl group having 1 to 5 carbonatoms; R₁ represents an alkylene group having 2 to 4 carbon atoms; R₂represents an alkylene group having 1 to 4 carbon atoms; Z represents a1,2-epoxy, 1,3-epoxy, or 1,4-epoxy group; and a, b, and c are integerscorresponding respectively to contents in terms of % by mole of theconstituent units.
 4. The photosensitive resin composition according toclaim 3, wherein the alkali-developable photocurable copolymer resin andthe epoxy-containing copolymer resin further comprise 0 to 75% by moleof constituent units represented by formula (4) and 0 to 75% by mole ofconstituent units represented by formula (5):

wherein R represents hydrogen or an alkyl group having 1 to 5 carbonatoms, R₂ represents an aromatic carbon ring, R₃ represents an alkyl oraralkyl group, and d and e are integers corresponding respectively tocontents in terms of % by mole of the constituent units.
 5. A colorfilter comprising: a transparent substrate; a colored layer provided onthe transparent substrate; and a protective layer provided so as tocover the colored layer, said protective layer having been formed bycoating the photosensitive resin composition according to claim 3 or 4,exposing the coating, developing the exposed coating with an alkali, andheating the developed coating.